Definition of Arithmetic Sequences and Series

A sequence is an ordered list of numbers and the sum of the terms of a sequence is a series. In an arithmetic sequence, each term is equal to the previous term, plus (or minus) a constant. The constant is called the common difference (d). The formula for finding any term of an arithmetic sequence is where a is the first term of the sequence, d is the common difference, and n is the number of the term to find. To find the sum of a certain number of terms of an arithmetic sequence use where Sn is the sum of n terms, a is the first term, and an is the nth term. An arithmetic sequence graphs as points along a line.